Apparatus and method for producing tires of different types simultaneously

ABSTRACT

An apparatus for producing tyres of different types simultaneously includes a central processing unit, work stations, and local processing units. The central processing unit causes sequential execution of a plurality of operating steps at the work stations according to one or more predetermined sequences of types of tyres. Each work station includes at least one operating unit. A local processing unit is associated with each work station. The local processing units associated with the work stations identify types of tyres corresponding to supporting members for the tyres. The local processing units associated with the work stations also select, from a predetermined group of operating procedures for each operating unit, a specific procedure for a type of tyre corresponding to a respective supporting member at a respective operating unit. A related method for producing tyres of different types simultaneously is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry under 35 U.S.C. § 371 fromInternational Application No. PCT/EP01/05844, filed May 22, 2001, in theEuropean Patent Office, the contents of which are relied upon andincorporated herein by reference; additionally, Applicant claims theright of priority under 35 U.S.C. § 119(a)-(d) based on patentapplication No. 00830385.1, filed May 26, 2000, in the European PatentOffice; further, Applicant claims the benefit under 35 U.S.C. § 119(e)based on prior-filed, copending provisional application No. 60/216,157,filed Jul. 3, 2000, in the U.S. Patent and Trademark Office.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plant and a method for producingtyres which are different from each other.

2. Description of the Related Art

A tyre for vehicle wheels normally comprises a carcass structure,essentially consisting of one or more carcass plies shaped in anessentially toroidal configuration and having their axially opposinglateral edges engaged with corresponding annular reinforcing structuresincorporating circumferentially inextensible inserts usually called“bead wires”. Each annular reinforcing structure is incorporated in whatis known as a “bead” formed along an inner circumferential edge of thetyre for fixing the tyre to a corresponding mounting rim.

A belt structure, comprising one or more strips of belt in the shape ofa closed loop, essentially consisting of textile or metal cords suitablyorientated with respect to each other and with respect to the cordsbelonging to the adjacent carcass plies, is applied to the carcassstructure in a radially external position.

A tread strip, normally consisting of a strip of elastomeric material ofsuitable thickness, is also applied to the belt structure in a radiallyexternal position.

It should be noted that, for the purposes of the present description,the term “elastomeric material” denotes the rubber mixture in itsentirety, in other words the whole material formed by at least onepolymer base suitably amalgamated with reinforcing fillers, and/orprocess additives of various types.

A pair of sidewalls, each of which covers a lateral portion of the tyrelying between what is called a shoulder area, located near thecorresponding lateral edge of the tread strip, and the correspondingbead, is applied to the opposite sides of the tyre.

Given the above, it should be noted that each type of tyre isessentially distinguished from the others by a set of chemical andphysical, structural, dimensional and appearance characteristics.

The chemical and physical characteristics essentially relate to the typeand composition of the materials, and particularly to the recipes of thevarious mixtures used in the production of the elastomeric materials.The structural characteristics essentially define the number and type ofthe structural components present in the tyre, and their positioningwith respect to each other in the structure of the tyre. The dimensionalcharacteristics relate to the geometrical measurements and to thecross-sectional profile of the tyre (external diameter, maximum chord orwidth, sidewall height and their ratio, in other words the sectionratio) and will be indicated simply as “specification” hereafter. Theappearance characteristics consist of the design on the rolling surfaceof the tread, the ornamental patterns and the various pieces of wordingor distinctive signs reproduced on the tyre, for example on thesidewalls of the tyre, and will be indicated as a whole as “treaddesign” in the remainder of the present description.

The conventional production processes essentially comprise four distinctsteps in the manufacture of tyres:

a) preparation of the mixtures,

b) production of the individual structural components,

c) assembly of the different structural components in succession, toproduce a crude tyre on a drum or other suitable support,

d) vulcanization of the crude tyre with simultaneous stamping of thetread design on the external surface of the tyre.

For the purposes of the present invention, “type of tyre” denotes a tyrehaving a given specification, given structural components of which itconsists, and a given tread design.

In an effort to reduce production costs, technological development hasbeen basically orientated towards the search for technical solutionswhich would lead to the production of increasingly fast and reliablemachinery, in such a way as to minimize the time required to produceeach tyre, while maintaining or improving the quality of the finishedproduct.

Thus, plants with high production capacity in terms of pieces producedper unit of time have been produced, using tyre manufacturing machinerywhich has reduced options for modification (or in other words, iscapable of producing only a limited range of types of tyre), but whichmaximize the serial production of tyres having identical structuralcharacteristics. Purely by way of example, in the most up-to-date plantsthe output can be up to approximately two carcass per minute, and theaverage batch output in one month of operation for each article (type oftyre) can be 3200 pieces, with an article-changeover time of 375minutes.

Attempts have also been made to reduce or eliminate the storage of thesemi-finished products present between one and another of the fourprocess steps listed above, in such a way as to minimize the costs andproblems involved whenever the type of tyre in production has to bechanged. For example, the document EP 922561 proposes a method forcontrolling tyre production, in which, in order to reduce or eliminateboth the crude tyre storage time and the number of crude tyres beingstored, a complex vulcanizing unit is provided, with a number of mouldssuitable for constantly absorbing the output of the complex tyremanufacturing unit. The production of tyres of different types,particularly those having different specifications, is achieved byreplacing and/or adapting from time to time the machinery provided inthe complex tyre manufacturing unit, in conjunction with the replacementof the moulds in the complex vulcanizing unit.

The applicant has found that, in all cases, the production of the tyresentails costs which increase with the variety of types of tyre to beproduced: in particular, it is necessary to intervene in the processesand/or mixture production plants to permit the production of componentswith new and different physical and chemical characteristics and/or inthe production plants of the individual structural components to changethe specification of the tyres being produced. It is also necessary tochange the operating sequence (different assembly method) and/or theequipment and adjustment of the manufacturing machinery whenever achange is made in the structure and/or the specification of the tyre tobe produced. Finally, it is necessary to have at least one vulcanizingmould for each different tread design-specification pair.

All of the above entails continuing costs for the purchase of mouldswith different specifications and different tread designs, and ofdifferent equipment, costs for installing the latter, losses of outputdue to machine downtime (a change of process or equipment generallycauses machine downtime), and waste of material. For example, in thecase of continuous production of components, machine downtime ofdownstream plants and/or a change in the characteristics of thecomponents generates excess production which has to be rejected, sinceit is impossible to re-use it.

Given these circumstances, in the applicant's perception the productionof a large number of types of tyre in a single plant is generallyundesirable, particularly if the objective of minimizing costs is to bepursued. In fact, this objective is incompatible with a frequent changeof equipment and production processes. When production processes of theconventional type are used, the applicant has observed that, where thevolume of sales of each individual type is sufficiently high, the numberof the production plants can be multiplied in such a way as to make itpossible to produce a different type continuously in each plant, thusminimizing the aforesaid disadvantages. On the other hand, where thevolumes of sales forecast for specific types are not particularly high,for example on an annual basis, it is also possible in each case tocarry out the whole production for at least one year immediately andcontinuously, to contain the production costs for these types. Thissystem may, however, affect the quality of the sold product, and tendsto increase storage costs, since the products remain in stock for a longperiod. The risk associated with sales also increases, for example as aresult of unforeseen rapid obsolescence of the product, and there is anincrease in the financial costs of capital tied up in the stocks of theproduct and in the installation of the moulds which are to be used onlyfor the restricted period necessary to complete the production of theforecast reduced volume.

In order to tackle these problems, the applicant has already developed aproduction method in which each series of tyres identical to each otheras regards production is broken down into daily lots, each comprising aquantity of tyres sufficient to cover the daily output of one mould. Inthis way the production of tyres having different specifications and/ordifferent constructional characteristics is optimized by eliminating thestorage of large quantities of crude and vulcanized tyres. This methodis described in European patent application EP 875364 in the name of thepresent applicant.

In a tyre production plant, the step of vulcanization of the tyre iscarried out in a period which is essentially identical for ranges of allthe types of tyres, but on the other hand the tyre manufacturing timediffers considerably according to the type of tyre to be produced.Additionally, the application of even a single component takes differentlengths of time for different types of tyre.

This impedes a frequent change of type within the plant described above,since the creation of waiting times for the vulcanization step wouldoccur whenever a tyre to be vulcanized belonged to a different type fromthat preceding it in the crude tyre processing sequence.

Moreover, a frequent change of type of tyre within one processing batchalso entails a frequent change of the equipment for making the differenttypes, thus further increasing the waiting times.

For the purposes of the present invention, the term “serial processingplant” denotes a plant in which the individual steps of processing ofthe tyre are carried out in a fixed sequence, in other words in whicheach tyre processing step starts immediately after the preceding stephas ended.

The applicant has observed that, in a serial processing plant, the totalproduction process time is dependent on the slowest processing step.

For the purposes of the present invention, the term “critical processingperiod” denotes a processing period in which no changes are planned inthe equipment during the tyre processing sequence.

SUMMARY OF THE INVENTION

The applicant has tackled the problem of controlling the functions ofthe plant in such a way as to produce, within a single critical period,types of tyres which are different from each other, while minimizing thewaiting times which are due primarily to the difference in the rates ofthe crude tyre manufacturing steps between tyres of different types.

According to the present invention, the applicant has provided a tyreproduction plant in which different types of tyre can be produced withinthe same critical processing period without increasing the waitingtimes.

More particularly, the applicant has provided a plant for manufacturingcrude tyres of different types by the successive assembly of elementarycomponents on toroidal drums of predetermined dimensions. Therefore,once the number of tyres to be produced for each type within a criticalperiod has been decided, it is possible to determine a sequence forintroducing the different drums into the plant and a sequence for thevarious processing steps which make it possible to keep the average timefor producing the quantity of crude tyres for this critical periodessentially constant. In a plant of this kind, the processing and thesequence of depositing the various components on the drum are not thesame for all the types of tyre, and, at the same time, different typesof tyre are produced within the same critical period.

The tyre is assembled in successive workstations, in each of which oneof the said elementary components is deposited on the drum.

The applicant has provided a plant in which each work station iscontrolled by a local unit capable of recognizing the drum which arrivesat it, and consequently the type of tyre which is to be produced. Eachlocal unit communicates with a central unit of the plant which controlsthe passage of a drum from one workstation to the next and distributescontrol to the different work stations.

One aspect of the present invention relates to a plant for producingtyres of different types simultaneously, comprising a plurality ofoperating units operating in succession, and characterized in that itcomprises:

a central processing unit capable of causing the sequential execution ofa plurality of operating steps at work stations, each of which comprisesat least one of the said operating units, according to one or morepredetermined sequences of types of tyres,

a local processing unit associated with each work station and capable ofidentifying the type of tyre corresponding to a drum supplied to each ofthe said operating units, and of selecting one of a predetermined groupof operating procedures for each of the said operating units which isspecific to the type of tyre corresponding to the drum being worked on.

In particular, each drum comprises a code identifying the type of tyreto be produced on it.

In particular, each work station comprises at least one reader of thesaid code identifying the type of tyre.

Preferably, the said identification code is associated with a shaft ofthe said drum.

Preferably, the said code identifying the type of tyre is a bar code.

Preferably, the said reader of the said identification code isassociated with each operating unit.

Preferably, the said reader of the said identification code isassociated with a robotic arm of each operating unit.

In a further aspect, the present invention relates to a method formanufacturing tyres of different types in an automatic plant comprisinga plurality of operating units operating in succession, characterized inthat it comprises the steps of:

causing, in a central processing unit, the sequential execution of aplurality of operating steps in the said operating units, according toone or more predetermined sequences of types of tyres;

identifying the type of tyre corresponding to a drum supplied to each ofthe said operating units;

selecting, from a predetermined group of operating procedures for eachof the said operating units, a specific procedure for the type of tyrecorresponding to the drum being worked on.

Preferably, the said step of identifying the type of tyre comprises thereading of a code identifying this type associated with the drum beingworked on.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages will be made clear by thefollowing detailed description of the present invention, with referenceto the attached figures, provided solely by way of example and withoutrestrictive intent.

FIG. 1 shows a layout of the plant according to the present invention.

FIG. 2 shows schematically the steps of a tyre production processaccording to the present invention.

FIG. 3 shows schematically the connections between the units of theplant of FIG. 1.

FIG. 1 shows an embodiment of a plant for manufacturing tyres accordingto the present invention. The plant comprises a complex manufacturingunit 2 for the production of crude tyres, in which each tyre beingprocessed is manufactured by the assembly of its structural componentsin a predetermined. sequence, and a complex vulcanizing unit 3 in whicheach tyre arriving from the complex manufacturing unit 2 is vulcanizedwithin a corresponding mould 34, 35, 36, 37, 38, 39.

The complex manufacturing unit 2 comprises a plurality of work stations5, 6, 7, 8, 9, 10 arranged consecutively along a processing path,preferably of the closed loop type, shown for guidance by the arrows 11in the attached FIG. 1. This line also has a feed station 20, atemperature stabilizing device 21, a first holding station 22, amultiple holding station 23, a second holding station 24, a thirdholding station 25 and a terminal holding station 26.

The work stations 5, 6, 7, 8, 9, 10 are capable of operatingsimultaneously, with each operating on at least one tyre beingprocessed, to assemble at least one of its structural components on tothe tyre.

More particularly, during the assembly steps the various structuralcomponents used in the production of each tyre are conveniently engagedon a supporting member, preferably consisting of a toroidal support ordrum whose profile essentially reproduces the internal configuration ofthe tyre to be produced. This toroidal support is made in such a waythat it can easily be removed from the tyre when the processing has beencompleted.

At least a first and a second type of tyre can be treated simultaneouslyin both the complex manufacturing unit 2 and in the complex vulcanizingunit 3. By way of example, in the following description, with referenceto the layout shown in the attached FIGS. 1 and 2, two different typesof tyre, differing from each other in their dimensional characteristics,are treated simultaneously. Clearly, it is also possible to operatesimultaneously on a different number of types which may have, inaddition or as an alternative to dimensional differences, differences interms of structural components and/or chemical and physicalcharacteristics and/or appearance.

In the layout shown for guidance in the attached figures, the toroidalsupports are shown without distinction between them and the tyres beingprocessed which are engaged on them, and are identified by the letters Aand B, each of which denotes a specific type of tyre.

As may be noted, the tyres being processed are distributed along theline of the complex manufacturing unit 2 in such a way that thedifferent types A and B succeed each other in a pre-set sequence.Additionally, the pre-set sequence of tyres to be produced within acritical period can be divided into a plurality of series having thesame sequence of tyres or having a different sequence, according to thetypes which are to be produced in each series. In the example shown inFIG. 1, a series comprising six tyres, A, B, B, A, B, A, is distributedalong the line of the production plant 1. In this example, a total ofsix toroidal supports, on each of which a corresponding tyre ismanufactured, are therefore simultaneously operated within the complexmanufacturing unit 2.

It should be noted that, for the purposes of the present description,the term “series” denotes a set of tyres of different types or of thesame type, which follow each other in a predetermined sequence. In thecomplex manufacturing unit 2 it is possible to provide, for example, aplurality of series, each consisting of different types of tyre, whichadvantageously succeed each other cyclically, for example according tothe pattern A, B, A, B, or series each of which advantageously consistsof a tyre of a first type interposed between two tyres of a second type,or series each of which consists of tyres which are all of the sametype, or various combinations of the said sequences.

Devices for the functional transfer and movement of the tyres operate inthe plant to sequentially transfer each of the tyres being processed Aand B from one of the work stations 5, 6, 7, 8, 9, 10 of the complexmanufacturing unit 2 to the next, and to the complex vulcanizing unit 3.The said devices also functionally move the toroidal support during thedeposition of at least one of the said structural components.

This functional movement comprises a rotation of the toroidal supportabout its axis and a rotation and/or translation of this axis in space.

Preferably, these devices comprise one or more robotic arms R1, R2, R3,R4, R5, R6, R7 and R8, each of which is associated with at least one ofthe work stations 5, 6, 7, 8, 9, 10 and is capable of operating on theindividual toroidal supports A or B, to carry out the sequentialtransfer of each tyre being processed.

The tyre is fabricated by moving the toroidal support and orientating itin space and applying the extruded structural components thereon by bothcircumferential and axial deposition.

The said robotic arms advantageously support the said toroidal supportsso that they project, in other words by gripping them at only one sideon the axis of rotation, thus enabling the various components to bedeposited over the whole of the axial extension of the support which hasa curvature with two bends.

A processing unit commands the transfers along the said loop path anddetermines the number and composition of the said series of tyres withina desired critical period. This unit is capable of controlling the saidfunctional transfer and movement devices in such a way as to co-ordinatethe steps of processing on each type of tyre in the complexmanufacturing unit 2 and in the complex vulcanizing unit 3.

More particularly, in the illustrated embodiment there is a firstrobotic arm R1, movable along a guide structure 19 if necessary, andoperating between the complex manufacturing unit 2 and the complexvulcanizing unit 3, to pick up a finished tyre from the latter andtransfer it to the first work station 5, where the tyre is removed fromthe corresponding toroidal support by means of the robotic arm R8. Thetoroidal support A extracted from the tyre is then transferred by thefirst robotic arm R1 from the first work station 5 into the temperaturestabilizing device 21.

If the type to be produced requires the use of a toroidal supportdifferent from that which has been dismantled previously, the roboticarm R1 picks up the appropriate toroidal support from the feed station20 and inserts it into the temperature stabilizing device 21.

This device 21 is capable of bringing the toroidal support to apreferred temperature to permit the subsequent processing, andparticularly to promote the adhesion of the first layer of elastomericmaterial to the metal of the support. This temperature is preferably inthe range from 80° C. to 90° C.

A second robotic arm R2 serves to transfer the toroidal support from thetemperature stabilizing device 21 to the second work station 6 where thefirst constructional components of the tyre are assembled. The assemblyoperation may, for example, comprise the coating of the outer surface ofthe toroidal support A with a thin layer of airtight elastomericmaterial, usually called a liner, carried out by a liner processing unit61, and the application of any necessary elastomeric strips in the areascorresponding to the beads of the tyre, carried out by the stripprocessing unit 62, and/or the formation of an additional lining layermade from elastomeric material and laid on top of the liner, carried outby the sub-liner processing unit 63.

Preferably, at the second work station 6, and also at the remaining workstations 7, 8, 9, 10, the formation of each structural component of thetyre is carried out in conjunction with the previously described step ofassembly, by the processing of at least one basic semi-finished productwhich is identical for each type of tyre A or B and supplied in apredetermined quantity according to the type of tyre to be constructed.

In particular, at the second work station 6 the production of the liner,the elastomeric strips and/or the additional lining layer canadvantageously be carried out by winding at least one strip-shapedelement made from elastomeric material on to the toroidal support Abeing processed, in consecutively adjacent and if necessary also atleast partially superimposed turns, this element having a width, forexample, in the range from 0.5 to 3 cm, and being drawn directly from acorresponding extruder, from a reel or from other suitable feed devicesassociated with the second work station 6.

The winding of the turns can be advantageously simplified by giving thesecond robotic arm R2 the function of holding the toroidal support A, bymeans of suitable gripping and driving members, and making it rotateabout its own axis, thus moving it suitably in front of pressure rollersor equivalent application devices (not described) combined with feeddevices, in such a way as to produce a correct distribution of the stripelement with respect to the outer surface of the toroidal support. Forfurther details of the procedure for the application of the structuralcomponents on a toroidal support with the aid of a robotic arm,reference should be made to European Patent Application No. 98830762.5in the name of the present applicant, which is incorporated herein inits entirety by reference.

When the assembly of the components at the second work station 6 hasbeen completed, the second robotic arm R2 deposits the toroidal support,with the corresponding tyre under construction, at the first holdingstation 22. A third robotic arm R3 picks up the toroidal support fromthe first holding station 22 to transfer it to the third work station 7,where the structural components which contribute to the formation of thecarcass structure of the tyre are assembled.

More particularly, at the third work station 7 one or more carcass pliesare produced and assembled, together with a pair of annular reinforcingstructures in the areas corresponding to the beads of the tyre. In asimilar way to that described with reference to the operating stepscarried out at the second work station 6, each of these structuralcomponents is produced directly at the assembly step, using a basicsemi-finished product supplied in a predetermined quantity according tothe type of tyre being processed.

For example, the carcass ply or plies can be formed by sequentiallydepositing on the toroidal support a plurality of strip pieces, cutindividually from a continuous strip element formed by a band ofrubberized cords laid parallel to each other. In turn, each annularreinforcing structure can comprise a circumferentially inextensibleinsert consisting, for example, of at least one metal wire element woundin a plurality of radially superimposed turns, together with a fillerinsert of elastomeric material which can be made by applying an elongateelastomeric element wound in a plurality of axially adjacent and/orradially superimposed turns.

Each of the said continuous strip element, metal wire element andelongate elastomeric element, which form the basic semi-finished productto be used in a predetermined quantity to produce the correspondingstructural component, can be taken directly from an extruder, from areel or from other suitable feed devices associated with the third workstation 7.

For further explanations of the procedure for producing the carcassstructure, reference should be made to European Patent Application No.98830472.1 in the name of the present applicant, which is incorporatedherein in its entirety by reference.

In the layout shown in the attached figure, the third work station 7 isdesigned to produce carcass structures such as those described inEuropean Patent Application No. 98830662.7, also in the name of thepresent applicant, which is incorporated herein in its entirety byreference. The carcass structure described in this patent applicationcomprises two carcass plies, each consisting of a first and a secondseries of strip pieces deposited in an alternating sequence on thetoroidal support. A pair of annular reinforcing structures of the typedescribed previously is also provided in each bead of the tyre, each ofthese structures being inserted between the terminal flaps of thepieces, belonging to the first and second series respectively, andforming one of the carcass plies, together with an inextensible insertapplied externally with respect to the second carcass ply.

To facilitate the sequential assembly of the various structuralcomponents in the predetermined order, the third work station 7 is madeto be equipped with at least three different work stations designedrespectively for the deposition of the strip pieces (unit 71), of themetal wire element (unit 72), and of the elongate elastomeric element(unit 73), which operate simultaneously, each on a corresponding tyrebeing processed. Consequently, three tyres, even if they are ofdifferent types from each other, can be treated simultaneously in thethird work station 7, each of the tyres being sequentially transferredfrom one to another of the processing units until the carcass structurehas been completed. The sequential transfer of the tyres into thevarious processing units provided at the third station 7 can be carriedout by the third robotic arm R3, assisted if necessary by a fourthrobotic arm R4 and/or by any necessary auxiliary transfer devices and bythe multiple holding station 23, at which more than one toroidal supportcan be present at the same time. This system makes it possible tominimize the waiting periods when the tyre being processed in this workstation are of types which differ from each other; this is because it ispossible to use the multiple holding station 23 to carry out processingon types which require a longer time at the most favourable moment, byadvantageously altering the order of the sequence of arrival of. thetoroidal supports at the work station. In the attached FIG. 1, the unit71 for depositing the carcass plies is engaged with a type B tyre andthe unit 72 for depositing the bead wires is engaged with a type A tyre.

On completion of the carcass structure, the fourth robotic arm R4deposits the toroidal support at the second holding station 24.

The fifth robotic arm R5 picks up the toroidal support from the secondholding station 24, to carry it to the fourth work station 8, which inthe illustrated example is occupied by a type A toroidal support. At thefourth work station 8, the structural components serving to form what isknown as the belt structure of the tyre are produced and assembled. Inparticular, a first processing unit 81 provided at the fourth workstation 8 deposits, directly on the previously formed carcass structure,two under-belt strips extending circumferentially in the shoulder areasof the tyre. These under-belt strips can be extruded directly from anextruder and applied with the aid of pressure rollers or equivalentapplication devices. A second processing unit 82 forms a first andsecond belt strip on the carcass structure, each strip being formed bythe sequential deposition of strip pieces laid adjacent to each othercircumferentially, each piece being made by cutting to size a continuousstrip element consisting of a plurality of cords adjacent and parallelto each other and incorporated in an elastomeric layer. A furtherprocessing unit 83 forms a further belt strip winding a continuous cordin turns which are axially adjacent to each other and radiallysuperimposed on the underlying belt layers. Further details of apossible procedure for producing the belt structure are described inEuropean Patent Application No. 97830633.0, in the name of the presentapplicant, which is incorporated herein in its entirety by reference.

When the belt structure has been completed, the sixth robotic arm R6transfers the tyre being processed to the fifth work station 9. At thefifth work station 9, the toroidal support B is engaged by the roboticarm R6 with the aid of which a tread strip is applied, this tread stripbeing produced by the winding of at least one further elastomeric stripelement in consecutively adjacent and radially superimposed turningsuntil a tread strip having the desired configuration and thickness isobtained. In the illustrated example, the operation is carried out bytwo units 91 and 92. When the aforesaid operations have been completed,the sixth robotic arm R6 deposits the toroidal support at the thirdholding station 25.

The tyre is then transferred to the sixth work station 10, occupied by atype A tyre in the illustrated example. At the sixth work station 10,the toroidal support is engaged by the seventh robotic arm R7 whichcauses it to move suitably in front of corresponding processing units tocarry out the application of abrasion-resistant elements to the areascorresponding to the beads (unit 101), and the application of thesidewalls, which are also produced by winding at least one elastomericstrip in adjacent and/or superimposed turns (unit 102).

When this operation is finished, the seventh robotic arm R7 deposits themanufactured tyre at the terminal holding station 26, where the tyre isheld until it is transferred to the complex vulcanizing unit 3.

Each of the work stations 5, 6, 7, 8, 9, 10 not only has one or moreprocessing units, but also comprises a feed device for supplying thebasic elements required for the production of the correspondingstructural component, operating in conjunction with application devicespresent in the aforesaid units, which apply the basic element and/or theresulting structural component to the tyre being processed.

The complex vulcanizing unit 3 advantageously comprises at least one setof vulcanizing moulds 34, 35, 36, 37, 38, 39, the number of which isequal to the quantity of tyres included in the said series of tyresbeing processed in the complex manufacturing unit 2. In the illustratedexample, six vulcanizing moulds 34, 35, 36, 37, 38, 39 are provided,each corresponding to the specification of one of the types of tyremanufactured along the line of the complex manufacturing unit 2.

Preferably, the moulds 34, 35, 36, 37, 38, 39 are mounted on a rotatableplatform 30 which can be rotated with a step-by-step movement, in such away that the moulds are made to follow a path, within the complexvulcanizing unit 3, to bring them sequentially, one after the other,next to a loading and discharge station 40 for the tyres beingprocessed. This rotation preferably takes place with a first rotation ina first direction of rotation, followed by a rotation in the directionopposite the first. Alternatively, this rotation may be of the closedloop type.

Each of the moulds 34, 35, 36, 37, 38, 39 is fed with pressurized steamthrough a corresponding connecting line (not shown) extending radiallyfrom a central column in which steam supply devices, consisting of aboiler for example, are integrated or connected in another way. Thewhole rotatable platform 30 can advantageously be enclosed in aninsulated structure having at least one access aperture located next tothe loading and discharge station 40, in order to prevent excessivedissipation of heat to the exterior.

Advantageously, the transfer of the individual tyre being processed intothe corresponding moulds 34, 35, 36, 37, 38, 39 is carried out by therobotic arm R1 at a rate equal to the rate of completion of the crudetyres being processed in the work stations distributed along the line ofthe complex manufacturing unit 2.

The plant described by way of example operates in the following steps,shown schematically in FIG. 2 and associated with the movements of therobotic arms R1, R2, R3, R4, R5, R6, R7 and R8. In the figure, and inthe remainder of the present description, the steps identified by theletter T followed by a progressive number refer to the manufacturing ofa crude tyre, and the steps identified by the letter C followed by aprogressive number refer to the vulcanization of the tyre and to thedismantling of the toroidal support.

T1) The robotic arm R1 picks up a toroidal support, termed the “core”below, from the feed station 20, and inserts it in the temperaturestabilizing device 21.

T2) The core is extracted from the device 21 by the robotic arm R2 andis positioned in front of an extrusion head of the unit 61. The arm R2rotates the core in such a way that the extruder deposits a strip ofelastomeric material on the surface of the core.

T3) The robotic arm R2 positions the core in front of an extrusion headof the unit 62. The arm R2 rotates the core in such a way that theextruder deposits a strip of elastomeric material on the specifiedportion of the surface of the core.

T4) (optional) The robotic arm R2 positions the core in front of anextrusion head of the unit 63. The arm R2 rotates the core in such a waythat the extruder deposits a strip of elastomeric material close to thebeads of the core.

T5) The core is deposited by the robotic arm R2 at the first holdingstation 22.

T6) The robotic arm R3 picks up the core from the first holding station22 and inserts it into the carcass ply deposition unit 71, at which afirst layer of carcass ply pieces is deposited.

T7) The robotic arm R3 picks up the core from the carcass ply depositionunit 71 and inserts it into the bead wire deposition unit 72, withinwhich a pair of annular reinforcing structures is deposited on the corein the areas corresponding to the beads of the tyre.

T8) The robotic arm R3 picks up the core from the bead wire depositionunit 72 and deposits it in one of the locations of the multiple holdingstation 23.

T9) The robotic arm R4 picks up the core from the holding position 23and places it in front of an extrusion head of the elastomeric fillerdeposition unit 73. The arm R4 rotates the core in such a way that theextruder applies a strip of elastomeric material on the beads of thetyre being processed.

The preceding three steps can be repeated a number of times, accordingto the type of tyre which is being produced. For this purpose, themultiple holding station 23, having multiple locations, each capable ofholding one core, is provided, together with two robotic arms R3 and R4for producing the carcass structure.

T10) The robotic arm R4 deposits the core at the second holding position24.

T11) The robotic arm R5 picks up the core from the second holdingposition 24 and places it in front of an extrusion head of theunder-belt strip deposition unit 81. The arm R5 rotates the core in sucha way that the extruder deposits a strip of elastomeric material in theshoulder areas of the tyre.

T12) The robotic arm R5 inserts the core into the belt strip depositionunit 82.

T13) The robotic arm R5 picks up the core from the unit 82 and insertsit into the processing unit 83 which forms a further belt layer bywinding a continuous cord in turns axially adjacent to each other andradially superimposed on the underlying belt layers.

T14) The robotic arm R5 deposits the core back in the second holdingposition 24.

T15) The robotic arm R6 picks up the core from the second holdingposition 24 and places it in front of an extrusion head of theunder-tread strip deposition unit 91. The arm R6 rotates the core insuch a way that the extruder deposits a strip of elastomeric material onthe crown area of the tyre being processed.

T16) The robotic arm R6 places the core in front of an extrusion head ofthe tread strip deposition unit 92. The arm R6 rotates the core in sucha way that the extruder deposits a strip of elastomeric material on thecrown area of the tyre being processed.

T17) The robotic arm R6 deposits the core at the third holding station25.

T18) The robotic arm R7 picks up the core from the third holding station25 and places it in front of an extrusion head of the abrasion-resistantlayer deposition unit 101. The arm R7 rotates the core in such a waythat the extruder deposits a strip of elastomeric material on the beadsof the tyre being processed.

T19) The robotic arm R7 places the core in front of an extrusion head ofthe sidewall deposition unit 102. The arm R7 rotates the core in such away that the extruder deposits a strip of elastomeric material on thesides of the tyre being processed.

T20) The robotic arm R7 deposits the core at the terminal holdingstation 26.

The crude tyre is now complete; the subsequent steps are concerned withthe vulcanization of the tyre and its removal from the core.

C1) The robotic arm R1 picks up the core, with the crude tyremanufactured on it, and transfers it to the complex vulcanizing unit,and in particular into a vacant vulcanizing mould 39.

C2) The vulcanizer closes the mould and rotates by one position. Thetyre is vulcanized in the period of one complete rotation of thevulcanizing apparatus. At the end of each step of this rotation, each ofthe other moulds is loaded with a crude tyre to be vulcanized.

C3) The first robotic arm RI picks up the vulcanized tyre, together withthe corresponding toroidal support, from the mould 39, and deposits itat the first manufacturing station 5, in a station 16 for dismantlingthe toroidal support.

C4) The eighth robotic arm R8 removes the toroidal support and depositsit in a recovery station 28.

C5) The eighth robotic arm R8 picks up the vulcanized tyre and depositsit on a storage platform 14 where the manufacturing time to be matchedto the vulcanizing time.

In the preceding description, the production of two different types oftyres, A and B, was covered by way of example. The first type A relatesto a tyre having the 195/65 R15 specification, and the type B relates toa tyre having the 225/50 R16 specification. The type A comprises asingle layer of carcass plies, while the type B comprises a double layerof carcass plies. Because of the diversity of dimensions andconsequently the different volumes of the two different types, theprocesses carried out on type B require a longer time than the processescarried out on type A. However, while the processes at the first,second, fourth and fifth work stations are compatible with the totalcycle times, the process at the third work station 7, at which thecarcass structures are produced, is significantly different for the twotypes, particularly in that it requires the repetition of the depositionof a layer of carcass plies for type B.

If the processes described above were carried out in succession, itwould then be necessary either to extend the cycle times by adaptingthem to the type which requires the longer times, or to provide anadditional work station.

However, the pair of robotic arms R3 and R4 and the multiple holdingstation 23 are able to change the processing sequence.

For example, if the first tyre to arrive at the third work station 7 isa type B tyre, in other words the one requiring a longer processingtime, the pre-set processing sequence is modified. This is made possibleby the fact that some processes require a time shorter than the raterequired to keep the complex vulcanizing unit always supplied with atyre for each rotation of tyres produced previously by the plant can beplaced while they are waiting to be sent to the subsequent finishing andinspection steps.

The procedure for treating the individual tyres along the line of thecomplex manufacturing unit 2 is such that the deposition of a structuralcomponent can advantageously be carried out independently of thecompletion of the production of another component on the immediatelypreceding tyre in the production process. A characteristic of theinvention is that the structural components of the tyre are preparedessentially at the moment of their deposition, thus making it possibleto operate without previously stored semi-finished products, and toadapt each unit immediately to the type of tyre being processed, thusavoiding wastage of material.

Additionally, the operation of each of the processing units located atthe individual work stations 5, 6, 7, 8, 9, 10, and that of each of therobotic arms, is controlled by a programmable local processing unit, insuch a way that the quantity of basic semi-finished products supplied iscontrolled appropriately, together with the movement imparted to thetoroidal support, to ensure that the individual structural components ofthe tyres being processed are correctly formed. In particular, thislocal processing unit can be programmed in such a way as to adapt theoperation of the processing units of the robotic arms to the type oftyre being treated from time to time in each individual work station.

Moreover, in order to impart greater operating flexibility to the plant,without limitation to predetermined sequences of different types oftyre, provision is preferably made to associate each of the workstations 5, 6, 7, 8, 9, 10 with devices for identifying the type of tyrebeing processed, interacting with selection devices to determine thequantity of basic element to be used for producing each structuralcomponent in the work station in question. For example, theseidentification devices can advantageously comprise a reader of bar codesor other types of code associated with the toroidal support of the tyre,which can be identified, by means of suitable reading devices, by thelocal processing unit, for the purpose of selecting the quantity ofsemi-finished product, for example by using pre-set tables of values.

At the moment at which a tyre is transferred to any of the work stations5, 6, 7, 8, 9, 10, the bar code reader identifies the type to which thetyre belongs, enabling the local processing unit to set the operatingprogram of the work station in a suitable way, in addition or as analternative to the instructions received from the central unit.

In particular, FIG. 3 shows a layout which makes clear thecommunications between the central unit 111 and the local processingunits 106, 107 and 108 associated with each work station 6, 7 and 8.This figure shows only three work stations, particularly the second workstation 6, the third work station 7 and the fourth work station 8, inwhich the liner layer, the carcass structure and the belt structure areapplied respectively. A unit for producing semi-finished products 206 or207 or 208, otherwise known as a feed device for supplying the basicsemi-finished product to be placed on the drum, is shown within eachstation. In particular, at the second work station 106 this unit 206produces the elongate elastomeric element; at the third work station 107this unit 207 produces the continuous strip element formed, for example,from a band of rubberized cords parallel to each- other; and at thethird station 108 this unit 208 produces the continuous tape element,consisting for example of a plurality of cords adjacent and parallel toeach other and incorporated in an elastomeric layer.

Each of the units for producing the semi-finished products 206 or 207 or208 communicates with the respective local unit 106 or 107 or 108. Theprograms for placing the semi-finished products on the drum,corresponding to the types of tyre that can be manufactured in theplant, are loaded into each local unit associated with a work station. Adatabase 222 which can be interrogated by the central unit contains allthe programs for the placing of the various components for the types oftyres that can be manufactured in the plant. This data base is updatedwhenever a new type is produced.

In particular, the programs comprise instructions for the robotic armsconcerning the movement of the drum and instructions for the units forproducing the semi-finished products. These programs are made available,preferably when the plant is started up, to the local units according tothe operations which they are to carry out.

The flow of operations takes place in the following way:

The central unit 111 receives a production request which comprises thetypes to be produced and their measurements and quantity.

This unit prepares one or more series of tyres to be produced in acontinuous flow, and enables each work station, by means of acommunication with each local unit, to pick up a drum from a holdingstation, in such a way that the preset sequence is maintained. Thecentral unit also positions the correct moulds on the vulcanizationturntable for producing these types.

Each local unit recognizes the drum to be picked up by means of theaforesaid identification means located on the drums, for example theaforesaid bar code. The recognition of the drum and therefore of thetype of tyre to be produced enables the local unit to activate thecorrect program for the operation to be carried out on the drum of thework station in question. At the end of the operation, each local unitsends a signal to the central unit which monitors the flow of tyresbeing processed and which determines their advance from one work stationto the next.

For example, the said bar code may be located on a shaft of the saiddrum. The robotic arm picks up the drum by grasping it by means of thisshaft.

The devices for reading the said bar code are preferably associated witheach operating unit. Even more preferably, these devices for reading thesaid bar code are associated with each work station. Additionally, thesedevices for reading the said bar code can be associated with eachrobotic arm present at each work station.

The movement of the tyres being processed is advantageously managed inthe form of a continuous flow in which the complex manufacturing unit 2is directly connected to the complex vulcanizing unit 3, the sequentialtransfer of the individual tyres being carried out at a rate equal tothe rate of completion of the tyres in the complex manufacturing unit 2,thus advantageously eliminating the need for storing crude tyres instorage buffers provided between the complex manufacturing unit and thecomplex vulcanizing unit.

The possibility of changing the assembly sequence of the variousstructural components according to the type of crude tyre to be producedenables the average the rotatable platform 30. Thus it is possible torecover useful time for making the change in the sequence.

The processing time in each processing unit and the rate of transfer aredetermined according to the number of steps of movement required alongthe line of the complex vulcanizing unit 3, in such a way that each tyreA, B can remain in the complex vulcanizing unit for a time at leastsufficient to complete the vulcanization process.

For example, at the carcass structure production station (third workstation) type A requires a minimum processing time of approximately 1.5minutes, and type B requires a minimum processing time of approximately3 minutes, owing to the fact that this type requires a doubleapplication of the carcass plies, as described above.

At the work stations which apply the liner and sub-liner (second workstation), the belt structure (fourth work station), the sidewalls andthe abrasion-resistant strip (sixth work station), the (minimum)processing time is less than 2.5 minutes for both types A and B. Thework station which applies the tread strip (fifth work station) requiresa (minimum) processing time of approximately 2.5 minutes for both typesA and B.

The complex vulcanizing unit 3 has six vulcanizing moulds; to carry outvulcanization in the chosen conditions, each mould is required to remainin the vulcanizer for 15 minutes. To achieve this vulcanizing time whilethe rotatable support of the vulcanizer carries out six steps ofrotation, one cover has to be fed to the complex vulcanizing unit onceevery 15:6=2.5 minutes.

According to the data supplied above, this time is compatible with thetimes of the stations 6, 8, 9 and 10, while the third work station 7 iscritical, since type B requires a processing time here which is too longfor the desired rate.

In order to enable the third step to be carried out, a plurality ofseries of types which are initially fed to the complex manufacturingunit is provided.

Each series consist of a number of tyres equal to the number of thevulcanizing moulds.

Each series consists of three type A tyres and three type B tyres,according to a first order, defined as follows: A1 B1 B2 A2 B3 A3 (thenumbers 1, 2, 3 etc. associated with each type A, B in the sequenceidentify the succession in time of the different types of tyre fed inthe sequence).

After the application of the liner and the sub-liner (second workstation) the order in each series remains unaltered.

At the third work station, the processing sequence requires, forexample, the execution of the following consecutive steps:

1. production of the single carcass ply on A1; A1 continues to thefollowing work stations;

2. production of the first carcass ply on B1; B1 is put to wait in themultiple holding station 23;

3. production of the first carcass ply on B2; B2 is put to wait in themultiple holding station 23 (in a different location from that occupiedby B1);

4. production of the second carcass ply on B1; B1 continues to thefollowing work stations;

5. production of the single carcass ply on A2; A2 continues to thefollowing work stations;

6. production of the second carcass ply on B2; B2 continues to thefollowing work stations;

7. production of the first carcass ply on B3; B3 is put to wait in themultiple holding station 23;

8. production of the single carcass ply on A3; A3 continues to thefollowing work stations;

9. production of the second carcass ply on B3; B3 continues to thefollowing work stations.

After the third work station, the series has a second order, as follows:A1 B1 A2 B2 A3 B3; this second order is different from the initialorder. The number of steps carried out is nine; each step requires aprocessing time of 1.5 minutes, and therefore the total time for whichthe work station is occupied in applying the carcass structure on thesix tyres is 1.5×9=13.5 minutes. The total time is less than 15 minutes,representing the desired rate for the vulcanization of six tyres.

As a result of the pre-set order of the series, together with the stepscarried out at the third work station as described above, the time forthe production of the carcass structure on type B is no longer critical.

In this example, the order is not modified further at the following workstations, and the rate of 2.5 minutes is maintained in all the followingstations,since they all require a processing time which is less than orequal to 2.5 minutes.

Additionally, type A1 is ready for the following station after 1.5minutes, whereas another 4.5 minutes elapse between it and the next typeB1.

In the following processes, type A1 can be slowed by approximately 1minute, while the processing of type B1 has to be accelerated by 1minute. The slowing is carried out by the holding station 23, or byslowing the rate of application of one or more of the subsequentcomponents.

The acceleration of type B1 is achieved by carrying out the followingprocessing in the minimum time, particularly by carrying out theoperations of depositing the belt structure and sidewalls in 2 minuteseach.

The vulcanizing moulds are arranged in accordance with the second order,in other words in the sequence A1 B1 A2 B2 A3 B3, in such a way as toreceive type A where a vulcanizing mould for this type is provided.

The series follow each other along the manufacturing and vulcanizinglines until the end of the critical period, at which point the mouldscan be replaced if different types are to be produced in the followingcritical period.

With the procedure described above, within a critical period of, forexample, eight hours, 96 type A tyres and 96 type B tyres are produced.

In view of the above, for two types, such as A and B, it is necessary tospecify a series in which one type B is followed by at least one type A,such that the sum of the times for the processing of the type A tyres bya predetermined work station (for example that in which B undergoes thesame process at least twice) up to the end of the manufacturing of thecrude tyre is shorter than the average total time of the said processesby a time corresponding to the time difference between the types A and Bin the said predetermined step.

This makes it possible to carry out the processing step which requiresthe longest time without causing a delay in the execution of thefollowing steps.

A change in the order of the series at the third work station 7 whichforms the carcass structure was described above; the present inventionis also applicable to types of tyres which also differ from each otherin the deposition of other components, for example the belt structures.In this case, the sequence will also be modified at the fourth workstation 8, by providing a further multiple holding station.

More generally, according to the location of the critical step in theprocessing sequence, the work steps will be accelerated or the waitingtimes between the steps preceding or following the said critical stepwill be reduced, in such a way as to compensate for the excess timeintroduced by the critical step.

Where necessary, a special holding station can be provided.

In the plant according to the present invention, the pre-set series andthe modifications of the order of each series are made possible by thefunctional transfer and movement devices, particularly the robotic arms,which enable the processing steps to be disassociated from each other.This is because a change in the order of the series means that one typeof tyre follows a different processing path from that of another type.The functional transfer and movement devices make it possible, within asingle critical operating period, to use a number of pathssimultaneously, one for each type of tyre being processed.

Each series represents a time package of steps organized in paths, eachof these corresponding to one type of tyre produced. The path throughthe various processing steps determines the type of tyre manufactured.

Additionally, the numbers of the said holding stations, of the saidmoulds, and of the said functional transfer and movement devices canvary according to how many, and which, types of tyre are to be producedwithin a critical period, as well as in relation to the performance ofthe equipment used.

When required, it is also possible to reduce the effective time of thevulcanization process carried out on the individual tyres, for exampleby retarding the injection of the steam into the mould 34, 35, 36, 37,38, 39 after the tyre has been introduced into it. It is thereforepossible, alternatively, to set different effective vulcanization timesfor the various types of tyre being processed.

The present invention also makes it possible to eliminate or at least tominimize the downtimes on each occasion when a type of tyre beingproduced is changed.

This is because, in these cases, the toroidal supports and thevulcanizing mould suitable for the production of one type have to bereplaced with toroidal supports and the vulcanizing mould suitable forthe production of the new type.

This replacement, which, however, is required only when the dimensionaland/or tread pattern characteristics are changed, can be carried outwith minimal effect on output, by providing suitable equipment ifnecessary.

The invention therefore makes it possible to conveniently produce tyresin very small batches, down to a few units, without requiringsignificant increases in the unit cost of the tyres.

It is also possible to produce batches of tyres comprising tyres whichare all of different types from each other, without requiring changes inthe equipment which produces the crude tyres.

What is claimed is:
 1. An apparatus for producing tyres of differenttypes simultaneously, comprising: a central processing unit; a pluralityof work stations; and a plurality of local processing units; wherein thecentral processing unit causes sequential execution of a plurality ofoperating steps at the work stations according to one or morepredetermined sequences of types of tyres, wherein each work stationcomprises at least one operating unit, wherein a local processing unitis associated with each work station, wherein the local processing unitsassociated with the work stations identify types of tyres correspondingto supporting members for the tyres, and wherein the local processingunits associated with the work stations select, from a predeterminedgroup of operating procedures for each operating unit, a specificprocedure for a type of tyre corresponding to a respective supportingmember at a respective operating unit.
 2. The apparatus of claim 1,wherein the supporting members are toroidal supports or drums.
 3. Theapparatus of claim 1, wherein each supporting member comprises a codeidentifying the type of tyre corresponding to the supporting member. 4.The apparatus of claim 3, wherein the identifying code is associatedwith a shaft associated with the supporting member.
 5. The apparatus ofclaim 3, wherein the identifying code is a bar code.
 6. The apparatus ofclaim 1, wherein each work station comprises at least one reader of acode identifying the type of tyres corresponding to the supportingmembers for the tyres.
 7. The apparatus of claim 6, wherein one readerof the identifying code is associated with each operating unit.
 8. Theapparatus of claim 6, wherein readers of the identifying code areassociated with robotic arms corresponding to the work stations.
 9. Amethod for producing tyres of different types simultaneously,comprising: causing sequential execution of a plurality of operatingsteps at work stations according to one or more predetermined sequencesof types of tyres; identifying types of tyres corresponding tosupporting members for the tyres at operating units of the workstations; and selecting, from a predetermined group of operatingprocedures for each operating unit, a specific procedure for a type oftyre corresponding to a respective supporting member at a respectiveoperating unit.
 10. The method of claim 9, wherein a central processingunit causes the sequential execution.
 11. The method of claim 9, whereinlocal processing units associated with the work stations identify thetypes of tyres.
 12. The method of claim 9, wherein local processingunits associated with the work stations select the specific procedures.13. The method of claim 9, wherein the supporting members are toroidalsupports or drums.
 14. The method of claim 9, wherein identifying thetypes of tyres comprises reading a code identifying a type of tyrecorresponding to a respective supporting member.
 15. The method of claim14, wherein the identifying code is associated with a shaft associatedwith the supporting member.
 16. The method of claim 14, wherein theidentifying code is a bar code.